Sound system

ABSTRACT

A sound system having means for producing an envelope from an original sound signal fed to a sound transmission system, means for detecting the leading edge of the envelope, and means for instantaneously changing the amplitude of the original sound signal by modulating the original sound signal based upon the shape of the leading edge of the envelope.

United States atet Shiga et al.

SOUND SYSTEM 1 Feb. 29, 1972 Inventors: Takeo Shiga; Michio ()kamoto; Osamu [56] References cued Kohsaka, all of Kawasaki-shi, Kanagawa- UNITED S S PATENTS ken, Japan 2,863,999 12/1958 French ..250/27 Assignee: Nippon Columbia Kabushiki Kaisha,

T ky Japan Primary ExaminerKathleen H. Claffy Assistant ExaminerHorst F. Brauner Flled Sept' 1969 Attorney-Hill, Sherman, Meroni, Gross and Simpson Appl. No.: 861,406

\ [57] ABSTRACT Foreign Application Priority Data A sound system having means for producing an envelope from an original sound signal fed to a sound transmission system, Sept. 30, 1968 Japan ..43/11014 means for detecting the leading g of the envelope and means for instantaneously changing the amplitude of the US. Cl. ..179/1 D original sound Signal by modulating the original Sound Signal Int. Cl .1104! 3/04 based upon the shape of the leading edge of the envclope Field of Search ..179/1 D; 328/162, 163, l64;

332/37, 38 11 Claims, 20 Drawing Figures '7 MODULATOR a V in c I 6644/91/77 DE 7-5 TOE L/M/flQ 2 3 (a Q -fi/rFfef/vr/4roe I Dl Q Q 3 1 I a J I A FE E pa 525 rm roe 8/6 74 BL E I I K a 5 F1 i i 0/:F5/V 7/4 roe l I Patented Feb. 29, 1972 3,646,270

3 Sheets-Sheet 2 1 1 .40 a 1"T m i 44 V ri E Mm (A26) Patented Feb. 29, 1972 3 Sheets-Sheet 5 J1. -EH

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SOUND SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound system for recording and reproducing sound with high fidelity and more particularly to a sound system which compensates for transients due to the distortion caused by active and passive networks of an electroacoustic sound system.

2. Description of the Prior Art High-fidelity systems for recording and reproducing have been highly developed. However, certain disadvantages still exist such as limited frequency response noise and the like which cause the fidelity to be reduced.

Certain electrical reproducing systems have specific or peculiar tone color or timber due to an electronic circuit system as compared with that of the original sound.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved system for reproducing sound capable of producing and reproducing sound as accurately as possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a wave form diagram employed for explaining the present invention;

FIG. 2 is a systematic block diagram illustrating one embodiment of the present invention;

FIG. 3 is a systematic block diagram showing another embodiment of the present invention;

FIGS. 4A, 4B, 4C, 4D and 4F are respectively wave form diagrams for showing the outputs obtained at the respective points for showing the outputs obtained at the respective points of the embodiment depicted in FIG. 2;

FIGS. 5C, 56, SH, SI, SJ, SK, SL, SM and 5N are respectively wave form diagrams for showing the outputs obtained at the respective points of the embodiment depicted in FIG. 3;

FIG. 6 is a block diagram of a circuit according to the present invention; and

FIGS. 7A and 7B are respectively graphs for explaining the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Transient characteristics have not been considered in detail in prior art devices because it is difficult to consider them quantitatively.

Study of Sound transmission systems have shown that the amplitudes of aural signals are changed by a transducer such as a microphone or speaker and become reduced. At times the reproduced sound is not sharp and does not have a clear and crisp tone. These phenomena result because the sound is transmitted through the electric circuit.

In the present invention, the envelope of an aural signal is emphasized during the leading edges of its build up of the envelope and the sound components which are changed with time are corrected so that the listener receives the correct response. As a result, favorable effects can be obtained by controlling the slope of leading edge of sound wave to obtain a pleasing response.

In the attached drawings, FIG. 1 is a wave form for explaining the object of the present invention which allows the slope of leading edge of a sound wave to be controlled. In FIG. 1 the solid line portion shows an actual aural signal and the dotted line curve shows a corrected aural signal obtained according to the present invention.

In FIG. 2 example, one part of an aural signal a shown in FIG. 4A is applied to a buffer circuit 1 from a point a and is then applied to a detector circuit 2 to obtain at point b an envelope a; shown in FIG. 4B. The envelope is applied to a differentiator circuit 3 and is differentiated. The difierentiated output a obtained at a point c is shown in FIG. 4C. The differentiated output a is then amplified by an amplifier circuit 4 and its negative portion is clipped by a diode 5 to obtain at point d a waveform form (1 shown in FIG. 4D. The clipping level of the differentiated wave form 0 shown in FIG. 6D is suitably changed, as shown by a dotted line e in FIG. 4D, by varying the bias voltage applied to a slipping circuit 6 includes a diode 6D and a variable DC power source 6E and is connected between ground and the diode 5 to adjust the compensating effect. The obtained differentiated wave form has only a positive portion and is applied to a modulator circuit 7 to modulate the original aural signal a with the differentiated wave form a The wave form obtained at a point f is (1 shown in FIG. 4F. The aural signal pulse has its leading edge portion emphasized as shown by the dotted line in FIG. 4F.

FIG. 3 shows another example of the present invention in which similar numerals to those of FIG. 2 example designate similar elements.

A differentiated wave form a 'is shown in FIG. 5C and FIG. 3 is obtained from the differentiation circuit 3. This wave is supplied to, for example, a Schmitt limiter 8 which is adjusted to respond in a positive direction at a predetermined level. The Schmitt limiter determines the position of the sound wave at which emphasis of the leading edge begins. Then, a rectangular wave form a shown in FIG. 5G is obtained at a point g. The rectangular wave form a is applied to a differentiator circuit 9 and is imperfectly differentiated. An output wave 0, obtained from the difierentiator circuit 9 (at point h) is shown in FIG. 5H and it is noted that the trailing edge portion is elongated. The wave fonn a shown in FIG. 5H is then supplied to a diode 5 to obtain at a point i a wave form a.,', as shown in FIG. SI. The wave form a provided at the point i is then ap plied to a modulator 7. As a result, a wave form a shown in FIG. SJ is obtained at a point j.

In a modification, the rectangular wave form a from the Schmitt limiter 8 in FIG. 3 is supplied to another differentiator circuit 10 as shown in FIG. 3 and is differentiated completely. The output of the differentiator circuit 10 occurs at point k and its shape is shown as a in FIG. 5K. The differentiator output a is supplied to a bistable circuit 11 to provide an output a at a point as shown in FIG. 5L, the level and with or duration of which are determined by the bistable circuit 11. The output a from the bistable circuit 11 is then applied to an integration circuit 12. An output a obtained from the integration circuit 12 appears at a point m and shown in FIG. 5M. This signal is applied to the modulator to modulate the sound signal a. An output a shown in FIG. 5N from the modulator 7, appears at a point n. The leading edge of the aural signal wave form shown in FIG. 5N is suitably changed in form and length.

If the circuit described above is used in a transmission system for only one channel and spectra of sound signals passing through the transmission system include various signal components from relatively low-frequency to highfrequency bands, it is possible that unnecessary sound signals will modulate each other. To prevent this a plurality of filters 13, I4, 15 shown in FIG. 6 and in which the passband characteristics respectively vary between lowand high-frequency ranges are provided. The filters 13, I4, and 15, receive an input signal IS which is separated into a plurality of multiple channels each having a suitable frequency range. The separated channel signals are respectively applied to a plurality of envelope changing circuits 16, I6, 16" as the forms shown in FIGS. 2 0r 3.

During recording, the above circuits can be connected to compensate for the phenomenon for each musical instrument or singer, if desired.

The present invention emphasizes the leading edge or buildup portion of the envelope of the aural signal and the reproduced sound is clear. Also sound which is nearly equal to a natural or original sound can be reproduced. This effect is especially important with the frequency of sound having lower frequencies than 1,000 H We claim:

l. A sound system comprising:

a first means for detecting the envelope of an original sound signal;

a second means differentiating said sound envelope; and, a third means for receiving said original sound signal and modulating it by the output of said second means whereby the leading edge build up of said envelope of said original sound signal is accentuated.

2. A sound system is as claimed in claim 1 further including a limiting means between the second differentiating means and said third means.

3. A sound system as claimed in claim 1, including a trigger means mounted between said second and third means and receiving said differentiated signal to produce timing pulses which control the modulation of said of said original sound signal.

4. A sound system as claimed in claim 3, wherein a control means receives the output of said trigger means and supplies an output to said third means for controlling the modulation degree of said original sound signal.

5. A sound system as claimed in claim 4 wherein said control means includes a second differentiating circuit having a long time constant for differentiating said timing pulses so that they have an elongated trailing edge portion.

6. A sound system as claimed in claim 4, wherein said control means includes a third differentiating circuit, a bistable circuit and an integrator circuit connected in series controlling the modulaton degree of said original sound signal.

7. A sound system as claimed in claim 1 comprising means for frequency dividing said original sound signal into a plurality of signals with the spectra of said plurality of divided signals being different from one another, and a plurality of sound systems according to claim respectively receiving each of said plurality of divided signals.

8. A sound system as claimed in claim 7 including means for connecting the outputs from said plurality of sound systems.

9. A sound system comprising:

a first means for detecting an envelope from an original sound signal transmitted from a sound signal transmission means;

a second means for differentiating said envelope and for providing a differentiated waveform;

a third means for permitting passage only of the positive portion of said differentiated waveform; and,

a fourth means for receiving said positive portion of said differentiated waveform and for modulating said original sound signal with said positive portion of said differentiated waveform.

10. A sound system comprising:

a plurality of filters of differing pass bands connected to an input terminal;

a first sound system connected to the output of a first one of said filters and said first sound system comprising a first means for detecting an envelope of a sound signal, a second means difierentiating said sound envelope,

a third means for receiving the output of said first one of said filters and modulating it by the output of said second means whereby the leading edge of said sound signal is accentuated;

a second sound system connected to the output of a second one of said filters and said second sound system comprismg a fourth means for detecting an envelope of a sound signal,

a fifth means differentiating said sound envelope,

a sixth means receiving the output of said second one of said filters and modulating it by the output of said fifth means whereby the leading edge of said sound signal is accentuatedv 11. A sound system according to claim 10 further including means for combining the outputs of said first and second sound systems. 

1. A sound system comprising: a first means for detecting the envelope of an original sound signal; a second means differentiating said sound envelope; and, a third means for receiving said original sound signal and modulating it by the output of said second means whereby the leading edge build up of said envelope of said original sound signal is accentuated.
 2. A sound system is as claimed in claim 1 further including a limiting means between the second differentiating means and said third means.
 3. A sound system as claimed in claim 1, including a trigger means mounted between said second and third means and receiving said differentiated signal to produce timing pulses which control the modulation of said of said original sound signal.
 4. A sound system as claimed in claim 3, wherein a control means receives the output of said trigger means and supplies an output to said third means for controlling the modulation degree of said original sound signal.
 5. A sound system as claimed in claim 4 wherein said control means includes a second differentiating circuit having a long time constant for differentiating said timing pulses so that they have an elongated trailing edge portion.
 6. A sound system as claimed in claim 4, wherein said control means includes a third differentiating circuit, a bistable circuit and an integrator circuit connected in series controlling the modulaton degree of said original sound signal.
 7. A sound system as claimed in claim 1 comprising means for frequency dividing said original sound signal into a plurality of signals with the spectra of said plurality of divided signals being different from one another, and a plurality of sound systems according to claim 10 respectively receiving each of said plurality of divided signals.
 8. A sound system as claimed in claim 7 including means for connecting the outputs from said plurality of sound systems.
 9. A sound system comprising: a first means for detecting an envelope from an original sound signal transmitted from a sound signal transmission means; a second means for differentiating said envelope and for providing a differentiated waveform; a third means for permitting passage only of the positive portion of said differentiated waveform; and, a fourth means for receiving said positive portion of said differentiated waveform and for modulating said original sound signal with said positive portion of said differentiated waveform.
 10. A sound system comprising: a plurality of filters of differing pass bands connected to an input terminal; a first sound system connected to the output of a first one of said filters and said first sound system comprising a first means for detecting an envelope of a sound signal, a second means differentiating said sound envelope, a third means for receiving the output of said first one of said filters and modulating it by the output of said second means whereby the leading edge of said sound signal is accentuated; a second sound system connected to the output of a second one of said filters and said second sound system comprising a fourth means for detecting an envelope of a sound signal, a fifth means differentiating said sound envelope, a sixth means receiving the output of said second one of said filters and modulating it by the output of said fifth means whereby the leading edge of said sound signal is accentuated.
 11. A sound system according to claim 10 further including means for combining the outputs of said first and second sound systems. 